Welcome Guys !!
Here I am going to write the article about how to parse the JSON data that is retrieved from the API service provider.
I am developing a simple weather application and i am using the http://api.openweathermap.org service.
This service return JSON data of current weather information.
Queries for data can be sent on the following URL:
private static String BASE_URL = "http://api.openweathermap.org/data/2.5/weather?q=";
We are going to attach a query parameter like "Rome,IT" and it will return me the all required information :
The URL will look like :
http://api.openweathermap.org/data/2.5/weather?q=Rome,IT
We can cheak the JSON using the above URL
The formatted readable data can be found by copying the raw browser data and using .JSON formattor http://jsonformatter.curiousconcept.com.
{
"coord":{
"lon":12.5,
"lat":41.9
},
"sys":{
"message":0.1019,
"country":"Italy",
"sunrise":1388385449,
"sunset":1388418491
},
"weather":[
{
"id":500,
"main":"Rain",
"description":"light rain",
"icon":"10n"
},
{
"id":701,
"main":"Mist",
"description":"mist",
"icon":"50n"
}
],
"base":"gdps stations",
"main":{
"temp":281.26,
"pressure":1019,
"humidity":93,
"temp_min":280.93,
"temp_max":282.15
},
"wind":{
"speed":2.6,
"deg":30,
"var_beg":360,
"var_end":70
},
"rain":{
"1h":0.25
},
"clouds":{
"all":75
},
"dt":1388440902,
"id":3169070,
"name":"Rome",
"cod":200
}
Step1: First we are going to created a model class that will hold the each instance of parsed JSON info.
public class Weather {
double lon=0.0;
double lang=0.0;
String country="";
long sunrise=0;
long sunset=0;
String main="";
String description="";
String icon="";
double temp=0.0;
double pressure=0.0;
double humidity=0.0;
double temp_min=0.0;
double temp_max=0.0;
double speed=0.0;
double deg=0.0;
double cloud=0.0;
String name="";
}
Step 2: We are going to start a ASYNC task that will send the request to the server demanding the JSON.
public class JSONWeatherTask extends AsyncTask<String, Integer, String>{
@Override
protected String doInBackground(String... arg0) {
// TODO Auto-generated method stub
Weather weather = new Weather();
String data = ( (new WeatherHttpClient()).getWeatherData(arg0[0]));
System.out.println(data);
try {
weather = JSONWeatherParser.getWeather(data);
System.out.println(weather.lon);
System.out.println(weather.lang);
System.out.println(weather.country);
System.out.println(weather.sunrise);
System.out.println(weather.sunset);
System.out.println(weather.main);
System.out.println(weather.description);
} catch (JSONException e) {
e.printStackTrace();
}
return data;
}
}
Step 3: We are going to establish a HTTP URL Connection and read the required data returned using the input stream readers and store them in a String type.
This data in string form will be parsed by a simple Json Parser and required results will be displayed.
public class WeatherHttpClient {
private static String BASE_URL = "http://api.openweathermap.org/data/2.5/weather?q=";
private static String IMG_URL = "http://openweathermap.org/img/w/";
public String getWeatherData(String location) {
HttpURLConnection con = null ;
InputStream is = null;
try {
con = (HttpURLConnection) ( new URL(BASE_URL + location)).openConnection();
con.setRequestMethod("GET");
con.setDoInput(true);
con.setDoOutput(true);
con.connect();
// Let's read the response
StringBuffer buffer = new StringBuffer();
is = con.getInputStream();
BufferedReader br = new BufferedReader(new InputStreamReader(is));
String line = null;
while ( (line = br.readLine()) != null )
buffer.append(line + "\r\n");
is.close();
con.disconnect();
return buffer.toString();
}
catch(Throwable t) {
t.printStackTrace();
}
finally {
try { is.close(); } catch(Throwable t) {}
try { con.disconnect(); } catch(Throwable t) {}
}
return null;
}
}
Step 4: In the last we are going to parse result data retrieved and display this in our application.
NOTE : While updating the User Interface , always use a separate thread. The separate thread can be created using
runOnUiThread(new Runnable() {
public void run() {
}
}
public class JSONWeatherParser {
// We start extracting the info
private static JSONObject getObject(String tagName, JSONObject jObj) throws JSONException {
JSONObject subObj = jObj.getJSONObject(tagName);
return subObj;
}
private static String getString(String tagName, JSONObject jObj) throws JSONException {
return jObj.getString(tagName);
}
private static float getFloat(String tagName, JSONObject jObj) throws JSONException {
return (float) jObj.getDouble(tagName);
}
private static int getInt(String tagName, JSONObject jObj) throws JSONException {
return jObj.getInt(tagName);
}
public static Weather getWeather(String data) throws JSONException {
// TODO Auto-generated method stub
// We create out JSONObject from the data
Weather weather=new Weather();
JSONObject jObj = new JSONObject(data);
JSONObject coordObj = getObject("coord", jObj);
weather.lon=getFloat("lon", coordObj);
weather.lang=getFloat("lon", coordObj);
JSONObject sysObj = getObject("sys", jObj);
weather.country=getString("country", sysObj);
weather.sunrise=getInt("sunrise", sysObj);
weather.sunset=getInt("sunset", sysObj);
//We get weather info (This is an array)
JSONArray jArr = jObj.getJSONArray("weather");
// We use only the first value
JSONObject JSONWeather = jArr.getJSONObject(0);
weather.main=getString("main", JSONWeather);
weather.description=getString("description", JSONWeather);
return weather;
}
}
Note : Guys ... I have just written a sample parser which is quite simple and give you a basic idea how things work.
The post will be updated later with the entire application to download.
For Any further question or actual source code for the application ...
mail me at : ajayjaiswalhi@gmail.com
Thank You !!
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